Image Credit: Adam Taylor/ABCCastle returns with a new episode on May 3. To tide us over, we phoned Michael Trucco (Battlestar Galactica), who has the enviable/unenviable job of guest-starring as robbery detective Tom Demming, Beckett’s new love interest, for the remainder of the season before he heads to Vancouver to shoot his own series, USA’s new dramedy Facing Kate with Sarah Shahi (NBC’s Life, Showtime’s The L Word), in June. Note to future Castle guest stars: He reveals Nathan Fillion’s prank of choice.

ENTERTAINMENT WEEKLY: Why did producers think you were the right man for the role?
Michael Trucco: I wasn’t totally familiar with the show, but I know in a situation like this, the dynamic between the two leads is very important. It’s not unlike the situation when I came in to Battlestar Galactica. There’s a lot of parallels there because my character [Anders] also came in to thwart the relationship between the two leads on that show, much in the same way this one is designed to throw a wrench in the works. It’s a tightrope for a character to come into a show, especially one that has such a strong fanbase as Castle, one that is gaining such traction, one that is based heavily on the potential relationship between Castle and Beckett. So I tried to make this character really likable, really believable, so that the audience can relate to Beckett and her potential attraction. If you come off as smarmy or sleazy, you end up being the bad guy in the end, then it just feels like the audience gets cheated. So, I wanted to put a real challenge in front of the characters and say, “We kinda like this guy.” At least that’s what I’m hoping for.

I think you succeeded in your first episode, and you’re right: When a lead falls for someone who’s so clearly not worthy, if affects how much you like her. It’s too out of character.
Yeah. It’s also on the page. I like the scene where Demming checks with Castle to make sure there’s nothing going on between them. It’s sort of the guy code that he check with Castle when he’s starting to express his feelings for Beckett. That’s a stand-up guy. That’s the right thing to do.

Have you heard from fans on the street? What’s been the reaction?
Not necessarily on the street, it’s still early. I have this masochistic tendency to look online and check reaction when episodes like this air. You know, there’s something about the anonymity that can be brutal. [Laughs] Sometimes it is better out of sight, out of mind. There are such dedicated die-hard fans of the Castle-Beckett dynamic, you come in and upset that dynamic, and people react. That just speaks to the power of this show and the writing – people are that into it. But I think it’s been going both ways. The most important thing is to illicit some reaction, good or bad. If some people are repellent to me, so be it. If some people are attracted to me, great. At the end, that’s the object of entertainment – you want to provoke a reaction. Hopefully, we’ve achieved that.

Did you know about the sparring scene with Beckett when you signed on? No one could deny that was fun.
I didn’t. [Laughs] I think on my first day on set, I was doing a wardrobe fitting, and then this guy comes upstairs and goes, “Hey man, I’m Dennis, the stunt coordinator.” I went, “Okay, nice to meet you. What does that have to do with me?” I had no idea that there was going to be this extensive fight scene, this sparring MMA-style kicks and punches and blocks and grappling. It turned out to be a lot of fun. We had two or three days of actual off-set rehearsal, which is really rare for television, because in television, you’re moving all the time. That made a huge difference. By the time we shot it, we ramped up the speed and she was bringin’ it. A lot of what you see is Stana really tryin’ to knock my block off.

And how did you feel about fighting her?
[Laughs] It’s odd. I’m not accustomed to taking a swing at a woman’s head. That’s not in my DNA. That was my big fear, and I said that to the stunt coordinator. I go, “Dude, I don’t want to look like I’m going half-speed here and pulling my punches.” And he said, “She can take care of herself. Go for it.” He wasn’t saying swing at her, but he was saying we worked this out really well. You know where to place your punches. We got more and more comfortable and my speed started to pick up, and Stana is such a superb athlete that I think we really sold this fight. But yeah, it’s a little uncomfortable. Are we really trying to swing at each other here, or what are we doing? The whole purpose of that scene was that tango, this dance, this kind of chemistry. It was cool.

Will we see more sparring? Is that going to be their thing?
No. At least not as far I know.

You're booked through the end of the season [May 17]. Is there any chance of you returning in season 3?
I would say it's left open. There's no indication either way. I was contracted for the four episodes, but you never know. I'm certainly amenable to the idea. This is one of the most comfortable sets I've ever been on.

Did they do anything special to welcome you, to haze you?
When Nathan, Seamus Dever, and Jon Huertas tried to get me with the shock pen, I knew I was in the club. They go, "Hey, Trucco, come over here." Nathan hands me this pen, he goes, "Write down a number between 1 and 30." As soon as I clicked it, I knew exactly what it was, but the batteries were dead, so I foiled them. That's the initiation on the set. They do it to everybody else, too. Then Seamus looks at Nathan and goes, "Dude, did you change the batteries?" "'Did you change the batteries?' Why don't you just give it away?" It was hilarious.

What's it like playing a love triangle with Nathan? Does he play fair? I know that he's sort of an ad-libber.
Sort of an ad-libber? Nathan's obviously a sharp wit, right? So he buttons just about every scene differently every time we shoot it. That's a major element to the magic of that show. It's cool because Nathan and I kind of come from the same roots. We've got that interstellar rivalry going. He's got the Firefly thing, I’ve got the Battlestar thing. I’m like, “My spaceship can beat up your spaceship.” [Laughs] We kind of bring that element into it. If anything, I would love to be able to come back and have more of that kind of verbal play with Nathan’s character. There’s that moment in my first episode when Michael Ironside taps Castle on the head with a golf club, and I go, “What was that all about?” And he explains what it was and he checks his hair. I go, “No, it’s good.” That stuff we just put in on the spot.

What can you tease about what’s to come?
What I can tell you is that obviously, there’s some decisions to be made in terms of these relationships. Things start to ramp up, get heightened, and a major wrench gets thrown into the works… Hearts will be aching, that’s all I can say.

You’re also a guitarist in a band in real life. Will Castle see Demming play the guitar? I could see that killing him.
Great suggestion. Let me get on the phone. That has not been introduced into the story.

How will these two do battle?
Things get interesting… Demming at the core is a good guy, so I don’t think there’s anything devious in his intentions. But he likes a good fight. Demming is competitive and not afraid to go toe-to-toe.

You’re actually the son of a police officer. Did you incorporate any of that experience into the character?
You know what, my father was a detective for about 38 years out of his 40-year career. I had this revelation a couple of weeks ago on-set. I was talking on the phone in my trailer, and I looked in the mirror and I saw the badge clipped to my belt, a gun with a holster, and the suit and the tie with the jacket off, and it was just déjà vu. I remember that image so clearly from growing up. My dad would come home for lunch, take off his jacket, have the gun and the badge. I realized it was the first time in my career that I got to play a cop. I have a coffee mug that my dad gave me years ago that has the San Mateo police logo and my dad’s name on it, so I brought it to set and used it in a scene. I mean, you don’t see it, it’s not prominently featured, but I just wanted that connectivity. It’s kinda neat to be able to bring a symbol of his career into the first time I get to play a detective. It felt really comfortable. I like walking in the shoes of this character.

Before you go,tell me about Facing Kate.
We shot a 90-minute pilot, and we’re gonna shoot 11 more episodes for a 13-episode season. It’s a one-hour dramedy in the same tone as Castle and those shows on USA. They don’t take themselves too seriously, there’s always a little bit of a wink and a nod, which I like. Sarah Shahi plays Kate, a woman who was formerly an attorney and has now become a mediator. She’s fed up with the black-and-white world of law, one winner-one loser. She has that “Can’t we all get along?” mentality. She just lost her father. I play her ex-husband, Justin. I’m an assistant district attorney, so I’m very hardcore into law. There’s quite a dynamic between Kate and Justin because we are exes, but somehow we always end up in bed together.

That’s a nice twist.
What I like about it is that it’s different than the standard male-female relationship where they start to get to know each other, then it’s will-they-or-won’t-they? We pick up the series where they’ve already been there and done that, and now they have a history instead of a honeymoon phase. We explore life after the marriage, still dealing with the feelings and the baggage.

There’s no delicate way to put this, but is this the kind of series that will show the love scenes or will they just be implied?
I don’t know. I haven’t seen scripts beyond the pilot. That’s yet to be discovered.

What would be your preference?
[Laughs] That’s a loaded question. “I hope I could be in bed with every actress.” I’m a married man, come on… I don’t think it’s gonna be knockdown, drag-out sex scenes every week. I think they’ll address it very tastefully. I think you’ll see those characters struggling with their attraction and their relationship. I have a feeling it will get more complicated, that Justin, my character, might find himself in precarious situations with other women as well. I think. I can’t wait to see where they’re gonna go with it.